Climate Change

A lot of people today, including many scientists, are concerned about climate change. But what exactly is climate, and why are so many people worried about it changing?

What is climate?

Climate is the average weather in a particular area over a length of time. For example, if we take 30 years of daily temperature readings of a city and average them, the result is what climatologists call a "climate normal." If you listen to an evening weather report, the reporter might say something like, "Today the temperature reached 34 degrees. That’s 3 degrees higher than the normal temperature of 31." Climatologists obtained that normal temperature of 31 degrees by taking 30 years of temperature readings for that day and averaging them. The climate of a place is the averages of the different weather conditions (temperature, rainfall, wind) of that place.

Why are people worried about climate change?

Since the climate is the averages of weather conditions, each new weather condition that is different from the normal will make a small change in the climate. When the new condition is only a single random event (like one very hot day in the middle of winter), there is no reason to be concerned. If, however, we start to have a lot of abnormal weather conditions, we start to think that we are experiencing climate change. Many people are concerned about climate change because they are afraid it will cause serious problems for life on our planet, such as melting of the polar icecaps and the spreading of tropical diseases.

What causes climate change?

We are only beginning to understand why climate changes, but we know that the main causes are natural. Changes in the amount of energy released by the sun are one cause. Clouds are another cause. Humans also cause climate to change. Have you ever noticed that cities are usually warmer than the countryside around them? That is because factories and cars produce more heat, and also because asphalt and cement absorb heat better than plants and trees. Cities also produce a lot of air pollution that contributes to climate change. Humans also cause climate change in rural areas when they clear forests and plant crops. Different colored crops can change the amount of energy that is absorbed by vegetation. All this human activity on the surface of our planet can cause climate change.

The list below presents some of the reasons people have for being concerned about global warming. First rank the reasons from 1 (most important) to 7 (least important). Then work with three or four other students and try to reach a group consensus on how to rank the statements. Be prepared to present your group’s final rankings to the class.

____ Forests would be destroyed. Global warming would cause parasites from tropical areas to extend their range and attack forests in temperate zones. Some tree species in temperate zones would become extinct.

____ Some food crops would become smaller. Global warming would lengthen the growing seasons in Canada, Finland, Japan and other countries in the Northern Hemisphere. However, wheat, corn and other soybean crops would become smaller.

____ Rangelands would be harmed. Global warming would increase problems of drought and erosion, and increased fires would become a problem.

____ Sea levels would rise. Global warming would cause sea levels to rise and cause flooding in coastal areas and very serious damage in low-lying countries such as Bangladesh.

____ Tropical diseases could spread. Global warming could cause tropical diseases such as yellow fever and malaria to spread to a wider area.

____ Some animal and plant species would become extinct. Global warming would cause many animal and plant species to become extinct because warmer temperatures would cause their habitats to change or disappear.

____ Some islands might disappear. Global warming would cause the world’s oceans to rise, and some small islands, including the Caribbean Islands and archipelagos in the Pacific, might disappear.